1. Field of the Invention
The present invention relates to an apparatus and method for providing a Mobile Internet Protocol TeleVision (Mobile IPTV) service in a mobile communication system and a broadcasting system.
2. Description of the Related Art
Wired IPTV systems provide real-time broadcast services and Video-on-Demand (VoD) services. The real-time broadcast services are provided using a plurality of real-time broadcast channels. When channel switching is made from the current real-time broadcast channel to a new real-time broadcast channel, a few seconds are required to receive data packets provided over the new real-time broadcast channel and decode the received data packets, causing a delay in the channel switching. Many different ways to minimize the switching time required for switching between real-time broadcast channels have been proposed, and a detailed description thereof will be made below.
Data packets being provided in real-time broadcast channels, such as adjacent real-time broadcast channels like the real-time broadcast channels whose channel numbers are just above and below a channel number of the current real-time broadcast channel presently providing a real-time broadcast service, or real-time broadcast channels whose channel numbers include a channel number corresponding to a specific number on a remote controller, which has been pushed by a user, are received in advance and then buffered. Thereafter, if channel switching is made from the current real-time broadcast channel to a new real-time broadcast channel, one of the adjacent real-time broadcast channels, the real-time broadcast channels may be switched without the switching delay.
In order to switch real-time broadcast channels without switching delay for all real-time broadcast channels, including the real-time broadcast channels whose channel numbers are just above and below a channel number of the current real-time broadcast channel, data packets corresponding to a predetermined buffering capacity should be received in advance and then buffered, for all the real-time broadcast channels provided by the wired IPTV systems.
As for the real-time broadcast channels, because data packets being provided over them may be decoded in advance through increases in hardware and computations of receivers, the switching time required for switching between the real-time broadcast channels is relatively short. However, in case of the VoD services, because the number of their available content channels is much greater than the number of real-time broadcast channels and it is difficult to predict which content channel a user will select, the time period required between the time the user selected a specific content channel and the time the specific content channel actually starts playing the content, is relatively long.
In the wired IPTV systems, in order to reduce the switching time required for switching between content channels, data packets being provided in content channels having a high correlation with the content being played in the current content channel are buffered in advance, and if new content channels, whose data packets have been buffered in advance, are selected, the data packets having been buffered are played immediately. This method will be described below with reference to FIG. 1.
FIG. 1 schematically illustrates a process of playing content upon switching of content channels in a general wired IPTV system.
The process, illustrated in FIG. 1, of playing content channels upon switching of content channels is a content playing process, in which for example, the content being played in the current content channel is a live baseball game in which a specific baseball player called ‘Lion King’ takes part, and channel switching is made to a content channel having a high correlation with the live baseball game, i.e., a new content channel in which videos of previous games, where the specific baseball player participated in, are played.
Referring to FIG. 1, while the current content channel plays a live baseball game of the specific baseball player, content having a high correlation with the content being played in the current content channel, for example, data packets provided in new content channels providing videos of previous games of the specific baseball player are buffered in advance.
As illustrated in FIG. 1, correlations between content being played in the current content channel and content to be played in the new content channels should be managed in a hierarchical manner to enable channel switching from the current content channel to the new content channels. However, in order to manage correlations between contents in a hierarchical manner, a database for the correlations between contents should be built, and additional overhead is required, such as transmission/reception of the correlation information.
Unlike the content channel switching method described in FIG. 1, a new method has been proposed, which switches content channels by buffering in advance data packets provided in new content channels existing in upper/lower tree menus of the menu in which the current content channel is included, using the characteristics that in case of VoD services, content thereof is likely to be selected according to the given menus.
Although the above-described real-time broadcast channel switching method and content channel switching method may reduce the switching time, unicast transmission or multicast transmission for transmitting data packets each user terminal will buffer in advance for the reduction in the switching time may continue to occur.
This continuous unicast transmission or multicast transmission is not a big problem in the wired environments where the sufficient transmission bandwidth and sufficient transfer rate may be guaranteed, like in the wired IPTV systems, so the real-time broadcast channel switching method and content channel switching method, in which the unicast transmission or multicast transmission continues to occur, may be used in the wired IPTV systems without significant problems.
However, if the real-time broadcast channel switching method and content channel switching method used in the wired IPTV systems are used in the wireless environments where the communication capacity and transmission bandwidth are limited, like in Mobile IPTV systems, use of which has been greatly increased recently, then the number of user terminals to which a Mobile IPTV service can be provided by the Mobile IPTV systems is limited due to an increase in the unicast transmission.
Therefore, the real-time broadcast channel switching method and content channel switching method used in the wired IPTV systems can hardly be used intact in the Mobile IPTV systems, leading to the necessity for a new real-time broadcast channel switching method and content channel switching method capable of minimizing the switching time.